北美洲古人类克劳维斯人灭绝消失，一直是科学界的谜团。科学家最近指出，于北美广泛地区的泥土中发现纳米钻石，引证于公元前1.1万年发生一场彗星撞击地球的毁灭性灾难，不单摧毁克劳维斯文化，也令长毛象和乳齿象等巨型生物瞬间灭绝。
科学家在2日出版的《科学》杂志发表有关研究报告，指出在北美洲多个地点的泥土中，均发现肉眼无法看见的纳米钻石，其中一处更是位于亚利桑那州梅利泉的克劳维斯遗址之上。研究员指出，纳米钻石需要在宇宙爆炸造成的高温和高压环境下形成。
科学家肯尼特说：“除了外层空间的力量，没有其它理由能够解释这些钻石的出现。”他指这次彗星撞地球，类似约6500万年前令恐龙绝种的彗星撞击。北美史前人类克劳维斯人在1.3万年前突然消失，长毛象、乳齿象、短面熊齿兽、剑齿虎和巨犰狳等古生物也绝种。（生物谷Bioon.com）
生物谷推荐原始出处：
Science 2 January 2009: DOI: 10.1126/science.1162819
Nanodiamonds in the Younger Dryas Boundary Sediment Layer
D. J. Kennett,1* J. P. Kennett,2 A. West,3 C. Mercer,4 S. S. Que Hee,5 L. Bement,6 T. E. Bunch,7 M. Sellers,7 W. S. Wolbach8
We report abundant nanodiamonds in sediments dating to 12.9 ± 0.1 thousand calendar years before the present at multiple locations across North America. Selected area electron diffraction patterns reveal two diamond allotropes in this boundary layer but not above or below that interval. Cubic diamonds form under high temperature-pressure regimes, and n-diamonds also require extraordinary conditions, well outside the range of Earth's typical surficial processes but common to cosmic impacts. N-diamond concentrations range from 10 to 3700 parts per billion by weight, comparable to amounts found in known impact layers. These diamonds provide strong evidence for Earth's collision with a rare swarm of carbonaceous chondrites or comets at the onset of the Younger Dryas cool interval, producing multiple airbursts and possible surface impacts, with severe repercussions for plants, animals, and humans in North America.
1 Department of Anthropology, University of Oregon, Eugene, OR 97403, USA.
2 Department of Earth Science, University of California, Santa Barbara, CA 93106, USA.
3 GeoScience Consulting, Dewey, AZ 86327, USA.
4 National Institute for Materials Science, Tsukuba 305-0047, Japan.
5 Department of Environmental Health Sciences/Center for Occupational and Environmental Health, University of California, Los Angeles, CA 90095–1772, USA.
6 Oklahoma Archeological Survey, University of Oklahoma, Norman, OK 73019, USA.
7 Departments of Geology and Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA.
8 Department of Chemistry, DePaul University, Chicago, IL 60614, USA.
